Predict the result
Consider x less than or equal to one.
Predict whether one is included and whether the ray points left or right.

Set up the model
Less than or equal to includes the boundary value one.
The smaller numbers are to its left. A square bracket at one includes that endpoint.

Work the example
This illustration shows the source’s left ray with an included endpoint at one.
An equivalent interval is open parenthesis, negative infinity, comma, one, close square bracket.
This interval notation is added for the opening; it describes the same set as the source graph.

Check the result
Now graph the same-lesson Try It: x less than or equal to negative one.
Choose the ray direction, decide whether negative one is included, and give the interval.
Take eight seconds to think before the answer.
[Eight-second silent pause to work; the answer remains hidden.]
Point the ray left and include negative one with a square bracket.
The equivalent interval is open parenthesis, negative infinity, comma, negative one, close square bracket.

Interpret the result
Both inequalities include their finite boundary. The square bracket shows that inclusion.
Negative infinity is not a number that can be reached or included as an endpoint.
Use a parenthesis at negative infinity and a square bracket at the included finite boundary.